Re: Two instances with same SID in a same machine

From: Mark Bole <makbo_at_pacbell.net>
Date: Fri, 27 Aug 2004 02:14:04 GMT
Message-ID: <MNwXc.12684$MF1.443@newssvr29.news.prodigy.com>

Howard J. Rogers wrote:
> Firehawk? wrote:
>
>

>>Is it possible ?
>>I am debating this question with a job partner.
>>My opinion is if I use two diferents Oracle users  like oracleA and
>>oracleB and make two instalations wholly separated, it's possible and to
>>attach to instances use differents listeners ports.
>>Am I correct ?

>
>
> I suppose knowing the proposed platform and O/S would be out of the
> question?
>
> Instance names must be unique on a host. How else can Oracle distinguish
> between them? How else can your O/S cope?
>
> For example, the rule about what file Oracle looks for at instance startup
> is that it searches ORACLE_HOME/dbs (or O_H\database) for a file called
> initSID.ora, or spfileSID.ora. Now, if you've two instances of the same
> name, that can only be because the ORACLE_SID environment variable is set
> identically... care to speculate on how one could find one initSID.ora, and
> the other could find a completely different initSID.ora, yet of the same
> name and in the same directory???
>
> Nice idea, but your opinion is, in this case, ill-founded.
>
> Regards
> HJR
>

Well, let's ask some questions. Could two different OS login users each have their own shared memory and semaphores? (assume some flavor of Unix, maybe under Windows too?) Check.

Could two different OS users each have an ORACLE_HOME (base directory) at different places in the server filesystem, independent of each other?   Check.

Could one physical server have several TCP/IP addresses? Check.

Could two listeners run on the same machine, each using port 1521 but a different TCP/IP address? Check.

I don't have the means readily at hand to test this right now (oh, where have you heard that before? ;-) ), but I think it can be done.

--Mark Bole Received on Thu Aug 26 2004 - 21:14:04 CDT